Apply correct casts to check_ext_mail and check_ext_mail_status

As always, the funcion pointers should be cast to the correct type before calling them, rather
than calling them with the wrong type and trying to cast the result.  Fixes a warning compiling
mail.c on 64 bit architectures, and this might well have caused a crash when using the qmail plugin
on those architectures too.

Changelog

@@ -1,5 +1,9 @@
 [Changes 1.2.2]
 
+* Cast check_ext_mail and check_ext_mail_status function pointers to the
+  correct type before using them. This might have caused a problem with
+  the qmail plugin on 64 bit architectures. (caf)
+
 * Fix bug in DCC privileged port detection logic. (caf)
 
 * Don't show DCC "Handshake failed" message twice, improve the message itself

source/mail.c

@@ -87,8 +87,8 @@ int count_maildir_mail(void)
 
 
 #ifdef WANT_DLL
-#define check_ext_mail global_table[CHECK_EXT_MAIL]
+#define check_ext_mail ((char *(*)(void))global_table[CHECK_EXT_MAIL])
-#define check_ext_mail_status global_table[CHECK_EXT_MAIL_STATUS]
+#define check_ext_mail_status ((int (*)(void))global_table[CHECK_EXT_MAIL_STATUS])
 #endif
 
 /*
@@ -111,7 +111,7 @@ static time_t old_stat = 0;
 struct stat stat_buf;
 #endif        
 #ifdef WANT_DLL
-	if (check_ext_mail)
+	if (check_ext_mail_status)
 		return (*check_ext_mail_status)();
 #endif
 	if (!get_int_var(MAIL_VAR))
@@ -182,7 +182,7 @@ static	char ret_str[12];
 static  int	i = 0;
 #ifdef WANT_DLL
 	if (check_ext_mail)
-		return (char *)(*check_ext_mail)();
+		return (*check_ext_mail)();
 #endif
 	switch (get_int_var(MAIL_VAR))
 	{